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Title: Discovery of a stripped red giant core in a bright eclipsing binary system
Authors: Maxted, P. F. L.
Anderson, D. R.
Smalley, B.
Burleigh, M. R.
West, R. G.
Collier Cameron, A.
Heber, U.
Geier, S.
Kupfer, T.
Gänsicke, B. T.
Marsh, T. R.
Nelemans, G.
O'Toole, S. J.
Østensen, R. H.
First Published: 1-Dec-2011
Publisher: Oxford University Press (OUP), Royal Astronomical Society
Citation: Monthly Notices of the Royal Astronomical Society, 2011, 418 (2), pp. 1156-1164
Abstract: We have identified a star in the Wide Angle Search for Planets (WASP) archive photometry with an unusual light curve due to the total eclipse of a small, hot star by an apparently normal A-type star and with an orbital period of only 0.668 d. From an analysis of the WASP light curve together with V-band and IC-band photometry of the eclipse and a spectroscopic orbit for the A-type star we estimate that the companion star has a mass of 0.23 ± 0.03 M⊙ and a radius of 0.33 ± 0.01 R⊙, assuming that the A-type star is a main-sequence star with the metallicity appropriate for a thick-disc star. The effective temperature of the companion is 13 400 ± 1200 K from which we infer a luminosity of 3 ± 1 L⊙. From a comparison of these parameters to various models we conclude that the companion is most likely to be the remnant of a red giant star that has been very recently stripped of its outer layers by mass transfer on to the A-type star. In this scenario, the companion is currently in a shell hydrogen-burning phase of its evolution, evolving at nearly constant luminosity to hotter effective temperatures prior to ceasing hydrogen burning and fading to become a low-mass white dwarf composed of helium (He-WD). The system will then resemble the pre-He-WD/He-WD companions to A- and B-type stars recently identified from their Kepler satellite light curves (KOI-74, KOI-81 and KIC 10657664). This newly discovered binary offers the opportunity to study the evolution of a stripped red giant star through the pre-He-WD stage in great detail.
DOI Link: 10.1111/j.1365-2966.2011.19567.x
ISSN: 0035-8711
eISSN: 1365-2966
Type: Journal Article
Rights: Archived with reference to SHERPA/RoMEO and publisher website. This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2011 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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